This invention relates to rotary valves for internal combustion engines and, more particularly, to a novel and highly-effective rotary valve characterized by (a) side-face seals of superior sealing ability, (b) longitudinal strip seals that are individually straight despite the angular offset of the valve from one cylinder to the next, (c) a duct portion that serves also as a portion of the combustion chamber and that produces a "squish" effect during the compression stroke, whereby greater turbulence of the fuel-air mixture and better burning are achieved, (d) impeller blades within the rotating part of the valve for producing a mixing and supercharging effect, and (e) exceptional durability and efficiency.
Rotary valves for internal combustion engines have long been known. They have certain obvious advantages as compared to poppet valves. Poppet valves have a reciprocating motion, which is a great drawback during high-speed operation. The inertia of a poppet valve can be reduced by making the valve lighter, but only to a point. The valve must have a certain minimum size (diameter, rise and thickness) in order to provide a sufficient cross-sectional flow area, to dissipate heat, and to withstand mechanical stress.
Despite the obvious advantages of rotary as compared to reciprocating motion, especially at high speeds, poppet valves have found much greater acceptance heretofore than rotary valves. That is because rotary valves in the forms in which they have existed heretofore have had drawbacks even more serious than those of poppet valves.
A principal drawback of earlier rotary valves has been the sealing problem. A rotary valve comprises an outer metallic stationary support member formed with a hollow interior, and an inner metallic member housed within the hollow interior and mounted for rotation about an axis. The outer support member and inner rotatable member are formed with ports and ducts for selectively enabling and preventing the flow of intake and exhaust gases through the valve in accordance with the angular position of the inner rotatable member with respect to the outer support member. It is essential to prevent or minimize leakage of gas between the stationary and rotatable parts of the valve during the times when the valve is closed and ensure that all the flow is through the intended channel when the valve is open. To this end, and in view of unavoidable manufacturing tolerances between the metallic stationary and rotating parts of the valve, special seals are necessary. This is in contrast to poppet valves in which the valve head seats without appreciable sliding and special seals are unnecessary.
The seals of a rotary valve are subject to unfavorable conditions. Engine temperatures are high, and so is the pressure within the combustion chamber, especially during the power stroke, when the intake and exhaust ports are both closed and the pre-compressed fuel-air mixture is in the process of rapid combustion. The seals must contain this pressure in order to ensure that the available energy is transferred to the piston with maximum efficiency.
A problem of long standing with conventional internal combustion engines, regardless of the type of valve employed, has been uneven distribution of fuel in the fuel-air mixture from one point to another in the combustion chamber. A relatively small quantity of fuel is mixed, by a process involving aspiration or injection, with a much larger quantity of air. The fuel is introduced into the air at a specific location and must be dispersed or distributed uniformly throughout the volume of air if the nominal fuel-air ratio is to represent not just a statistical average but the actual ratio at each point in the combustion chamber. Various designs have been employed in an effort to realize this objective, but the objective remains elusive.
Another problem of long standing with conventional internal combustion engines, regardless of the type of valve employed, has been a limitation on the amount of air that can be inducted or injected, which in turn limits the amount of fuel that can be introduced in accordance with the prescribed fuel-air ratio and thus also limits the maximum power of the engine. The air-induction limitation depends on ambient air pressure and on engine design and speed. The current accepted solution to the problem is turbocharging--a process by which engine exhaust gas or another source of power drives an impeller in the air-intake system to force additional air into the engine. Turbocharging is used especially in high-performance cars and piston-engine aircraft. However, turbocharging adds considerably to the initial cost of the basic engine and to the cost of maintenance. For this reason, it has not found acceptance except in special situations where high performance is mandatory.
Moreover, rotary valve designs have in the past been inefficient because of their complicated design and excessively subject to bearing failure because of excessive temperatures and insufficient lubrication.
Examples of prior attempts to improve the design of rotary valves include those described in a patent to Lockshaw U.S. Pat. No. 4,016,840 and a patent to Guenther U.S. Pat. No. 4,036,184. Both patents relate to implementation of the stratified-charge principle. The latter patent discloses a rotary valve operating at one-quarter engine RPM and having a diametral connecting duct between the intake manifold and the combustion chamber. A separate and isolated diametral conducting duct is provided for the exhaust gases, and these ducts are remote from one another. U.S. Pat. No. 4,016,840 discloses a valve body that also operates at one-quarter engine RPM and a central exhaust conduit that precludes exhaust tuning. The valve body diameter must be large in order to accommodate a central exhaust conduit and a water jacket surrounding it and to provide adequate flow area for the intake ducts surrounding the water jacket. As a result, the valve is necessarily relatively heavy and expensive.